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July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi1 A new proposal to measure O(100) events of K +   +  at the CERN SPS Riccardo Fantechi INFN - Sezione.

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Presentation on theme: "July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi1 A new proposal to measure O(100) events of K +   +  at the CERN SPS Riccardo Fantechi INFN - Sezione."— Presentation transcript:

1 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi1 A new proposal to measure O(100) events of K +   +  at the CERN SPS Riccardo Fantechi INFN - Sezione di Pisa On behalf of the P326 Collaboration CERN, Dubna, Ferrara, Firenze, Frascati, Mainz, Merced, Moscow, Napoli, Perugia, Protvino, Pisa, Roma, Saclay, Sofia, Torino _

2 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi2 Outline Physics motivations The goals The beam The detector

3 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi3 Physics motivations K + →  + : process predicted with high accuracy –Short distance only –No EM penguins –Matrix element derived from experiment (K + →  0 e   –There is an intrinsic theoretical error of 5-7% on the amplitude, due to charm quark loops, which can be reduced to few % BR(K + →  + ) = (8.0  1.1)  10 –11 in the NLO Constrain the CKM triangle only from the Kaon sector, together with future K 0 →  0  experiments _ _ _

4 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi4 Possibly the Cleanest SM test In the phase  derives from Z 0 diagrams (  S=1) whereas in A(J/  K S ) originates in the box diagram (  B=2) Any non-minimal contribution to Z 0 diagrams would reflect on a violation of the relation: A deviation from the predicted rates of SM would be a clear indication of new physics Complementary programme to the high energy frontier: –When new physics will appear at the LHC, the rare decays may help to understand the nature of it

5 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi5 Some BSM Predictions SM8.0 ± 1.1 MFV hep-ph/ EEWP NP B ± 2.1 EDSQ hep-ph/ MSSM hep-ph/

6 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi6 K + →  +  : State of the art BR(K + →  + ) = × Compatible with SM within errors hep-ex/ , PRL93 (2004) Stopped K ~0.1 % acceptance  k,  m d,sin(2  ) (All  F=2 processes) 3 events from E events, SM100 events, E949 value _ _

7 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi7 Prospects on K + →  + Decays at rest: –Window of opportunity to accumulate more data at BNL until 2010 (before KOPIO data taking starts) –Letter of intent for an experiment with stopped kaon decays at JPARC (>2009) –Established technique… –…but hard to extrapolate to O(100) events Decays in flight –Large acceptances, good photon rejection –Separated beam: FNAL CKM (Approved but Not Ratified) Limited to about P K <30 GeV/c –Un-separated beam: FNAL-P940 (now canceled) –Un-separated beam: CERN-P326 (expected data in 2009) Limited by rate in beam trackers _

8 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi8 P326 - The goal Collect 80 K + →  +  events in about two years of data taking for: –4  Kaon decays/SPS year –BR( K + →  +  ~ –Acceptance ~ 10% Decay in flight, unseparated beam –Higher K momentum Larger yield of K decays Better veto performance –Higher acceptance –Different systematics –Disadvantage:  /K ratio ~ 10/1 1 Ghz rate in the beam tracker ahead of the decay volume Keep pions and pion decays inside a “beam pipe” Region I Region II K →K → K  →   K →K → K →K → _ _

9 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi9 Background reduction Main background from K  2 and K + →  +  0 3 handles for background reduction: –Missing mass cuts –Photon vetoes –Particle identification Redundant measurements to control the background

10 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi10 Kinematics Measured quantities Resolution and MS tails for two and three body decays Cut on m 2 miss around   mass and on m 2 miss >0 –To have a S/N 10/1, need to cut at  m 2 ~ 8  GeV 2 /c 4 Need a resolution of ~ GeV 2 /c 4 –On  momentum  <1% a 30 GeV/c redundant  momentum measurement with tracker in vacuum –On K momentum: 0.3% performant beam tracker –On K-  angle   rad Contributions to background rejection 5  to K + →     2  to K + →  

11 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi11 Vetoes Advantage using high momentum –75 Gev/c K + and  + momentum < 35 Gev/c, then 40 Gev of EM energy to be detected Require at least rejection for  0 Low energy, large angle photons (low inefficiency) correlated with high energy ones at small angle Wide coverage of the photon angles –Hermetic up to 50 mrad –Few blind zones where photons are correlated with high energy ones at small angles –Possible to have an average  0 inefficiency of better than Use different devices for different angles –Small calorimeters to cover the hole inside the LKr calo –The LKr calorimeter itself for up to 15 mrad –13 annular calorimeters (either lead/scintillator or lead/sci fibers calorimeters) along the decay region »Inefficiency for low energies (< 1Gev/c) photons shown to be enough (10 -4 )

12 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi12 Particle ID Electron ID from the NA48 Liquid Krypton calorimeter –Reject K e3, K e4 Muon ID from EM, mu+hadronic calorimeter –Reject K  2, K  2 , K  3 –A RICH is needed to have redundant measurement and improve rejection Require at least a rejection factor of 10 5 on muons

13 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 13 Beam: Present K12 (NA48/2) New HI K + > 2006 Factor wrt 2004 SPS protons per pulse on T101 x x Duty cycle (s./s.)4.8 / Solid angle (  sterad)  0.40  Av. K + momentum (GeV/c)6075 Total : 1.35 Mom. band RMS: (  p/p in %)  4  1 ~0.25 Area at Gigatracker (cm 2 )  7.0  20  2.8 Total beam per pulse (x 10 7 ) per Effective spill length MHz MHz/cm 2 (gigatracker) ~45 (~27) ~16 (~10) Eff. running time / yr (pulses)3* x * K + decays per year1.0x x10 12  40 New high-intensity K + beam for NA48/3 Already Available

14 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 14 P326 Detector Layout 800 MHz (  /K/p) Only the upstream detectors Are exposed to the 800 MHz beam 10 MHz Kaon decays K+K+ ++ 1.5 m

15 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 15 Detectors CEDAR –Differential Cherenkov counter for positive kaon identification GIGATRACKER –To Track the beam before it enters the decay region ANTI –Photon vetoes surrounding the decay tank SPECTROMETER –2 magnets + 6 straw chambers to track the kaon decay products RICH –For redundant muon/pion separation CHOD –Fast hodoscope to make a tight kaon-pion time coincidence (~100 ps) LKR –Forward photon veto and e.m. calorimeter MAMUD –Hadron calorimeter, muon veto and sweeping magnet SAC –Small angle photon vetoes Challenging detector! Ineff for E  >100 Mev Ineff for E  > 1 Gev Ineff for E  > 6 Gev Ineff. 1 Gev electron inefficiency Get rid of the tails form MS Inefficiency: Inefficiency: 10 -5

16 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 16 Gigatracker Challenging beam tracker ahead of the decay region Specifications: –Momentum resolution to ~ 0.5 % –Angular resolution ~ 10  rad –Time resolution ~ 100 ps –Minimal material budget –Perform all of the above in 800 MHz hadron beam, 60 MHz / cm 2 Hybrid Detector: –SPIBES (Fast Si micro-pixels bonded to r/o ICs) Momentum measurement Facilitate pattern recognition in subsequent FTPC Time coincidence with CHOD –FTPC (NA48/2 KABES micromegas technology with FADC r/o) Track direction

17 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 17 Time Schedule 2004 –Parasitic tests in NA48/2 beam done –Startup of working groups –Submission of a Letter of Intent for the Villars meeting 2005 –Gigatracker R&D started –Preparation of the proposal –Proposal submitted to SPSC –Evaluation process for the proposal started –Costruction, Installation and beam-tests –Data Taking From the Villars report to the SPSC

18 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi18 Conclusions An experiment to measure the decay in flight K + →  +  is being proposed at CERN The goal is to collect O(100) events in 2 years The experiment will use some of the existing facilities of NA48 –It is not definitely a continuation of NA48 There are new detectors with challenging aspects The Collaboration is being formed _

19 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi19 Spares

20 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi20 Physics Introduction: CKM matrix and CP-Violation N g =2 N phase =0  No CP-Violation N g =3 N phase =1  CP-Violation Possible Quark mixing is described by the Cabibbo-Kobayashi-Maskawa (CKM) matrix KM mechanism appears to be the main source of CP-violation in quarks: Direct-CP Violation exists:  ’/   0 NA48, KTeV CP violation in the B meson sector: A CP (J/  K s ), BaBar, Belle Now look for inconsistencies in SM using independent observables affected by small theoretical uncertainties and different sensitivity to new physics e.g. Im t = Im V ts *V td ≠ 0  CP KM mechanism:

21 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi21 Kaon Rare Decays and the SM (holy grail) Kaons provide quantitative tests of SM independent from B mesons… …and a large window of opportunity exists! |V td | G. Isidori Im t = A 2 5  Re t = A 2 5 

22 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi22 K→  : Theory in Standard Model charm contribution top contributions The Hadronic Matrix Element is measured and isospin rotated (~10% correction)

23 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi23 Predictions in SM Error ~ 14% Mainly parametric Theory error due to charm (Buras04): Largest contribution from scale error. To be reduced by NNLO calculation The error is almost purely parametric For long distance contribution see:"LIGHT-QUARK LOOPS IN K->PI NU NU" By G. Isidori, C.Smith, F.Mescia. e-Print Archive: hep-ph/

24 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi24 BR(K L    )  5.9 x (  0  ee , 1997 Data) [PRD 61, (2000)] BR (K L    )  1.6 x (  0  , Day) [PLB 447, 240 (1999)] K 0 L    State of the Art Data MC BG Sum   n   MC     MC Signal MC KTeV 1997 Data Dalitz Analysis Still far from the model independent limit: BR(K 0 →  0 ) < 4.4 × BR(K +  + ) ~ 1.4 × Grossman & Nir, PL B407 (1997)

25 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi25 Prospects K 0 L    –Large window of opportunity exists. –Upper limit is 4 order of magnitude from the SM prediction –Expect results from data collected by E391a (proposed SES~ ) –Next experiment BNL K 0 L    ee(  ) –Long distance contributions under better control –Measurement of K S modes by NA48/1 bound the K L measurement –K S rates to be better measured (KLOE?) –Background limited (study time dep. Interference?) –100-fold increase in kaon flux to be envisaged K +    –The situation is different: 3 clean events are published –Experiment in agreement with SM –Next round of exp. need to collect O(100) events to be useful –Move from stopped to in flight experiments

26 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 26 Message from the CERN Director General to the staff (Jan 05) The top priority is to maintain the goal of starting up the Large Hadron Collider (LHC) in 2007 “…Meanwhile, the natural break we have in the fixed-target programme in 2005 is already allowing the community to develop a well- focused programme for the future” The possible Non-LHC Future Programme was reviewed by the SPSC in Villars (September 22-27, 2004)

27 John Dainton Villars 2004 October 7th 2004 CERN seminar ● new rare decay frontier in K physics at CERN ● new experiments planned for K  πνν important ● support R&D now for K +  π + νν results ≤ 2010

28 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 28 From the Villars Report… CERN-SPSC SPSC-M-730 February 28, 2005

29 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi29 Riduzione del background Taglio sulla m 2 miss intorno alla massa del  0 –Inefficienza sui veti di –Inefficienza sui  di 5  –Rapporto S/N 10/1 con accettanza >1 –Il taglio intorno alla massa del     m 2 ~ 8  GeV 2 /c 4 Risoluzione necessaria ~ GeV 2 /c 4 –Risoluzione impulso K: 0.3% –Risoluzione impulso  <1% a 30 GeV/c –Risoluzione angolo K-   rad Measured quantities

30 30July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi NA48/3 simulation NA48/3 simulation Uncorrelated non gaussian tails Gaussian MSC (old) Non-Gaussian MSC  P  (Spectrometer 1) GeV/c  P  (Spectrometer 2) GeV/c M(miss) 2 (GeV/c 2 ) 2 New MSC REGION I REGION II

31 31July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi Region I Region II P = [15- 35] GeV/c (RICH) 2.8 × 10  × 10  2 P = [ ] GeV/c 3.9 × 10  × 10  2 I+II (RICH) 70 events/year 4×10 12 BR = K + momentum: (75.0 ± 0.8) GeV/c Acceptance

32 32July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi Rapporti segnale/fondo * RICH Segnale: K + →  +  ( BR≈ 8.0 × ) BRVeto rej. rej.Kinem.Rej.AcceptanceBgnd     63 % 5 5   %(20%*)8(<1*)  21 % 3 3   %~1  6 % (2 (2  10 -5)20%~1  2 % < <10 -8 (2 (2  10 -5)15%<<1         3 % Non crea problemi Non crea problemi<<1   e    e  5 % e/p <10 -3 e/p <10 -3<<1

33 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 33 CEDAR K/  Cedar-W Cedar-N

34 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 34 8 Condensors “focus” the photons on the detectors (32-channel linear array multianode PM) Simulation allows to calculate the image size and to optimise location of the photon detectors Tagging eff. ≈ 90% Misident. prob. < 1% Tagging eff. ≈ 90% Misident. prob. < 1%

35 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 35 GIGATRACKER SPIBES1 SPIBES2 FTPC m momentum: use SP1 and SP2 to measure y = 40 mm displacement. Assuming σ p ~50µm from pixel and 350µm thick Si (0.37% X 0 ) σ = (σ p √2 ‡ σ MS ) ⁄ 40 mm = 0.25% direction: use SP2 and FTPC. Assuming σ p ~100µm from pixel and similar from FTPC and no MS from FTPC (from SP2 no influence) ∆  х = σ p √2 ⁄ 12.4m = 11µrad time resolution: essential to obtain a low background due to accidental hits and to allow the pattern recognition. Need 100 ps for S/B=10

36 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 36 FTPC (KABES+FADC) NA48/2 –KABES has achieved very good performance –Position resolution ~ 70 micron –Time resolution ~ 0.6 ns –Rate per micro-strip ~ 2 MHz NA48/3 –Intensity ~ 10 higher per unit area –600 ns drift –The long drift (600 ns) makes a standalone pattern recognition very difficult or just impossible ( That’s why we plan to have SPIBES in front) –To reduce double pulse resolution and improve the time resolution one has to reduce the pulse duration and possibly read-out every micro-strip with 1 GHz FADC

37 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 37 Doppio spettrometro

38 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 38 Perdita di accettanza dovuta al foro centrale: <10% Straw 2.3m, Ø9.6 mm Kapton films 12  m+25  m Ogni half-layer: 112 straws  per DCH: 4×4×112=1792

39 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 39 ≈ straws, 130  m di risoluzione per vista Doppio spettrometro

40 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 40 Set of ring-shaped photon vetoes surrounding the decay tank Specification: inefficiency to detect photons above 100 MeV < The NA48 ANTI’s (AKL) need to be replaced Extensive R&D performed by American and Japanese groups Claims that inefficiency as low as can be achieved Baseline solution: Lead/ Plastic scintillator sandwich (1-2 mm lead / 5 mm plastic scintillator) SPACAL (a la Kloe) option also being studied CKM design Anticontatori

41 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 41 Questo rivelatore deve consentire di vetare i  0, con inefficienza massima tollerabile ≈10 -7, ovvero, mediamente, dell’ordine di o meglio sul singolo fotone. Naturalmente, la capacità di veto dipende dall’energia del  e l’effetto complessivo richiede un’integrazione sull’accettanza, nonchè la combinazione con il segnale dal LKr e dai piccoli rivelatori (SAC e IRC) a piccolo angolo. Da una simulazione della cinematica, assumendo ragionevoli inefficienze per i vari rivelatori, si ottiene una inefficienza media per il  0 di circa dopo il taglio sull’impulso del  +. Il contributo maggiore all’inefficienza media viene dall’1% circa di fotoni che mancano i rivelatori Anticontatori

42 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 42 Soluzione alla CKM 1mm Pb/5 mm scintillatore (+WLS fiber) 80 layers, 16 X 0 13 corone circolari di 16 settori ( ) Superficie totale vista dai fotoni: 28 m 2 Superficie totale di Pb e Sci: 2270 m 2 Lunghezza delle fibre per la raccolta di luce: 220 Km 13 x 64 = 832 fototubi Montaggio tra due sezioni del tubo a vuoto in tasche sotto vuoto –Per mantenere il vuoto del tubo di decadimento migliore di mbar Anticontatori R ext = 1100 mm R int = 880 mm

43 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 43 Soluzione alla KLOE 0.5mm Pb/ 1mm fibre scintillanti Spessore 24 cm  20 X 0 13 corone circolari, in U o in anello (da studiare) Superficie totale del Pb: 5600 m 2 Lunghezza delle fibre: 4100 Km 96x13=1248 fototubi Anticontatori

44 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 44 L’idea è quella di usare Glass Multigap RPCs, sullo stile di quanto realizzato nel sistema di TOF di ALICE A questo rivelatore infatti è richiesto di essere efficiente (>99%) e di avere un’ottima risoluzione temporale (50ps) in modo da ridurre al massimo la possibilità di associazioni accidentali fra il pione di decadimento ed il K che lo origina. E’ necessario pero’ valutare l’ efficienza di questi rivelatori nelle zone piu’calde, dove il rate per unita’ di area e’ superiore a quanto finora provato da ALICE. Odoscopio veloce

45 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 45 ~80 K +  πνν p  ion NA48/3  COMPASS

46 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 46 4×2 modules, each equipped with horizontal and vertical strips, respectively. With strips 20x1280 mm 2 (20 = 19strip + 1 interstrip) the total number of channel is 60×4×2 = 480 ( ×2 …) The estimated material budget is ≈ 15% X0 2.4 m Odoscopio veloce - Struttura

47 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 47 LKR Calorimeter Must achieve inefficiency < to detect photons above 1 GeV –Need to take data in 2006 to measure the inefficiency It is needed to identify electrons Advantages: –It exists –Homogeneous (not sampling) ionization calorimeter –Very good granularity (~2  2 cm 2 ) –Fast read-out (Initial current, FWHM~70 ns) –Very good energy (~1%, time ~ 300ps and position (~1 mm) resolution Disadvantages –0.5 X 0 of passive material in front of active LKR –The cryogenic control system needs to be updated The readout electronics should be rebuilt

48 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 48 MAMUD Pole gap is 2 x 11 cm V x 30 cm H Coils cross section 10 cm x 20cm To provide pion/muon separation and beam sweeping. –Iron is subdivided in cm thick plates (260  260 cm 2 ) Two coils magnetise the iron plates to provide a 0.9 T dipole field in the beam region Active detector: – Strips of extruded polystyrene scintillator (1 x 4 x130 cm 3 ) – Only half the slots instrumented – Light is collected by WLS fibres with 1.2 mm diameter – Two planes of fast scintillator in the last part for a fast muon trigger

49 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 49 Trigger Il rate di traccia singola passa da 1 MHz (NA48/2) a circa 20 MHzIl rate di traccia singola passa da 1 MHz (NA48/2) a circa 20 MHz –10 dai decadimenti del K e 7 dall’alone del fascio –Necessita’ di un trigger di livello 0 con una reiezione di ~20 e poi utilizzo di un trigger software in una batteria di PC –Massima flessibilita’ nello sviluppo e aggiornamento degli algoritmi Con l’uso del segnale dell’ odoscopio, del mu e di depositi di energia in quadranti del calorimetro, si riesce ad ottenere la reiezione volutaCon l’uso del segnale dell’ odoscopio, del mu e di depositi di energia in quadranti del calorimetro, si riesce ad ottenere la reiezione voluta –Semplificazione del trigger veloce –Si evitano il piu’possibile correlazioni tra rivelatori diversi –Facilita’ di imporre offline tagli piu’severi

50 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 50 Trigger Limitare al massimo lo sviluppo di soluzioni ad hocLimitare al massimo lo sviluppo di soluzioni ad hoc –Molto e’stato sviluppato per LHC (LHCB, Alice, etc) –Necessita’ di uniformare I moduli di readout di tutti I rivelatori –Utilizzo di hardware commerciale (PC, Switch Eth Gb, etc) Quindi trigger di livello 0 semplice seguito da una farm di PCQuindi trigger di livello 0 semplice seguito da una farm di PC –Riduzione del rate in ingresso ai PC sotto il Mhz (come LHCB) –Trigger software sull’informazione completa –In totale canali Gigatracker e dalle camere a ridottissima occupazione Gigatracker e dalle camere a ridottissima occupazione canali del calorimetro compattati, con zero suppression fatta a software nei PC13500 canali del calorimetro compattati, con zero suppression fatta a software nei PC

51 July 23rd, 2005HEPP - EPS 2005 Riccardo Fantechi 51 Trigger


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